Temporal Variations in Hotspot Volcanic Production Caused by Interactions Between Upwelling Mantle Plumes and Phase Transitions
Abstract
Observations at numerous hotspots around the globe, such as Hawaii and Louisville, find periodic variations in volcanic production with time. For example, the volcanic production rate along the Hawaiian seamount chain varies from 0.05 to 0.25 km3/yr at periods of 15 Myr, while volcanic production rate along the Louisville seamount chain has consistently declined over the past 40 Myr. One possible explanation for these variations is long-term interaction of upwelling mantle plumes with mantle phase transitions. While previous studies carefully quantify the initial interaction and subsequent penetration or inhibition of a plume as it encounters the 660 km phase boundary and traverses the transition zone, the long-term interaction of plume upwelling and phase boundaries in the mantle is not well constrained. To assess the impact of plume-phase transition interaction on observed variability in hotspot volcanic output, we use the Advanced Solver for Problems in Earth's ConvecTion (ASPECT) code to numerically simulate upwelling of an isolated plume under the Anelastic Liquid Approximation (ALA). We use an axisymmetric 2D shell geometry with a 60° opening width and mantle thickness of 2855 km. Plume upwelling is initiated by imposing anomalously warm (ΔT 250 K) temperatures across a zone 200 km wide centered at the base of the model. At the 660 km and 410 km depth mantle phase transitions we simulate changes in density, viscosity, and the release of latent heat. Models are allowed to evolve for up to 1 Gyr. To test the effect of differing mantle compositions, we vary the Clapeyron slopes from 1 to 5 MPa and -0.5 to -6 MPa at the 410 km and 660 km phase transitions, respectively. Similar to other studies, results of preliminary simulations show an initial flattening of the plume head at the 660 km transition before penetration and subsequent acceleration across the 410 km transition, coinciding with mild shoaling of the 660 km, and deepening of the 410 km. Here, we will present analyses of mass flux periodicity and near-surface melt production rates and the implications on hotspot volcanic production rates.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFMDI11A0262N
- Keywords:
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- 1038 Mantle processes;
- GEOCHEMISTRY;
- 1140 Thermochronology;
- GEOCHRONOLOGY;
- 5430 Interiors;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS;
- 8121 Dynamics: convection currents;
- and mantle plumes;
- TECTONOPHYSICS